Rocket science

Launch a “rocket” indoors!

Difficulty:
Danger:
Duration:
10 minutes
Rocket science

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

How can I make the rocket fly as far as possible?

When placing the tube in the beaker, position it at a 45o angle.

The rocket isn’t taking off. What should I do?

First, make sure the rocket is placed on the stopper at the bottom of the beaker. Second, check that the capsule of citric acid is open. If all else fails, repeat the experiment using another test tube.

The rocket took off before I could put it in the beaker.

These compounds react very quickly and intensely. That's why you should prepare the beaker in advance – so that you can rapidly put the test tube in it.

Some of the contents of the test tube got on me. Are they safe?

Sodium carbonate and citric acid are often used in cooking. In case of contact with skin, rinse the affected area thoroughly with water.

Step-by-step instructions

Assemble the tail unit for your rocket.

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Add sodium carbonate Na2CO3 solution.

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Prepare a capsule of citric acid crystals.

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Put your citric acid capsule inside the rocket and seal the rear end.

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Let the citric acid react with the sodium carbonate by turning the rocket over.

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Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink and wash with an excess of water.

Scientific description

When we turn the test tube upside down, water begins to dissolve the sodium carbonate Na2CO3 and citric acid H3C6H5O7 powders. As these compounds dissolve, some charged particles called ions appear in the solution. One of these ions the CO32-  from the Na2CO3 reacts with H+  ions from the citric acid H3C6H5O7. This ion-exchange reaction produces water H2 and CO2  gas.

Why does the test tube launch into the air?

The test tube takes flight because of gas formed via a chemical reaction. As the tube is closed securely with a stopper, the gas accumulates there. Once a certain amount of gas accrues in the test tube, it erupts out, forcibly disconnecting the tube from the stopper. And we have liftoff!

Pressure: why is the tube forced out?

Initially, the tube contains only air. It consists of a large number of molecules, mostly nitrogen N2 and oxygen O2, which are constantly moving around. Air molecules move quite quickly, colliding amongst themselves and with surrounding objects. Luckily, they are very small, so we don’t feel these collisions on an individual basis, but we’re familiar with their cumulative result — pressure. Pressure, which is usually associated with the P symbol, is a characteristic that describes how many of these molecules collide with an object per time unit, and how quickly these molecules are moving during these collisions.

While gas starts forming and accumulating inside the tube, conditions outside the tube remain relatively unchanged. After a period of time, there are many more gas molecules inside the tube hitting the walls and the cap than outside the tube. We say that there is relatively high pressure inside the tube. And at some point, this pressure grows enough to overcome the force (known as friction) holding the stopper secure in the tube. And so the tube launches!

What is the gas we obtain and how does it form?

It is carbon dioxide CO2. Carbon dioxide forms when we mix sodium carbonate Na2CO3 and citric acid:

2H3C6H5O7 + 3Na2CO3 → 2Na3C6H5O7 + 3CO2↑ + 3H2O

More about the reaction:

When we turn the test tube upside down, the sodium carbonate Na2CO3 solution and citric acid H3C6H5O7 powder are mixed and the reaction begins. The following ions form:

Na2CO3 → 2Na+ + CO32–

H3C6H5O7 → 3H+ + C6H5O73–

H+ from citric acid and CO32– from carbonate react to yield water and carbon dioxide gas:

2H+ + CO32– → H2O + CO2

Such a reaction is known as an ion exchange reaction (as the substances quite literally exchange ions with one another).

Carbon dioxide gradually accumulates and noticeably increases the pressure inside the tube. As there is not enough space for the air and carbon dioxide molecules combined, they begin to push on the stopper and on the walls of the vial. At some point, the stopper can no longer contain the pressure, so it disconnects and comes to rest at the bottom of the beaker. There is nothing stopping the vial, though, which jets off like a rocket.

How does the tube fly? Do rockets fly the same way?

Actually, the tube flies rather like a cannonball shot from a certain angle into the air. Real rockets fly due to other physical processes that result when a huge volume of heated gas is released from the rocket nozzle. However, the driving force in a rocket also relies on another sort of chemical reaction known as an oxidation-reduction reaction.